Cellulose acylate film, optically compensatory film, polarizing plate and liquid crystal display

Abstract

A cellulose acylate film is provided and contains an additive. Tg of the cellulose acylate film is lower by 5 to 50° C. or the half value width of the diffraction peak at 2θ=10 to 15° in the X-ray diffraction pattern of the cellulose acylate film after heating at 200° C. for 3 hours is 110 to 300%, each compared with a cellulose acylate film not containing the additive. An optically compensatory film, and a polarizing plate and a liquid crystal display using the film are provided.

1 . A cellulose acylate film comprising an additive, the cellulose acylate film fulfilling at least one of requirements (1) and (2):
 (1) the cellulose acylate film has a glass transition temperature lower by 5 to 50° C. than that of a cellulose acylate film not containing the additive; and   (2) the cellulose acylate film having been heated at 200° C. for 3 hours has a half value width of a diffraction peak at 20 of 10 to 15° in an X-ray diffraction pattern thereof, the half value width being 110 to 300% of a half value width of a cellulose acylate film not containing the additive and having been heated at 200° C. for 3 hours, and   the cellulose acylate film further fulfilling numerical formulae (1) and (2):
   0 ≦Re   630 ≦10, and | Rth   630 |≦25  Numerical formulae (1) 
   | Re   400   −Re   700 |≦10, and | Rth   400   −Rth   700 |≦35  Numerical formulae (2) 
   
     wherein Re(λ) indicates an in-plane retardation by nm of the cellulose acylate film at a wavelength of λ nm; and Rth(λ) indicates a thickness-direction retardation by nm of the cellulose acylate film at a wavelength of λ nm. 
   
   
       2 . The cellulose acylate film according to  claim 1 , which has an absolute value of dimensional change after standing at 60° C. and 90% for 24 hours, the absolute value being 5 to 90% with respect to an absolute value of dimensional change of a cellulose acylate film not containing the additive. 
   
   
       3 . The cellulose acylate film according to  claim 1 , which has a modulus of elasticity of 101 to 150% with respect to a modulus of elasticity of a cellulose acylate film not containing the additive. 
   
   
       4 . The cellulose acylate film according to  claim 1 , which has a vapor transmission rate of 30 to 90% with respect to a vapor transmission rate of a cellulose acylate film not containing the additive. 
   
   
       5 . The cellulose acylate film according to  claim 1 , which has a contact angle after alkali saponification of 95% or less with respect to a contact angle after alkali saponification of a cellulose acylate film not containing the additive. 
   
   
       6 . The cellulose acylate film according to  claim 1 , which has a tear strength of 95% or less with respect to a tear strength of a cellulose acylate film not containing the additive. 
   
   
       7 . The cellulose acylate film according to  claim 1 , which has a coefficient of humidity expansion of 95% or less with respect to a coefficient of humidity expansion of a cellulose acylate film not containing the additive. 
   
   
       8 . The cellulose acylate film according to  claim 1 , which is obtained from a starting polymer having an acylation ratio of 2.85 to 3.00. 
   
   
       9 . The cellulose acylate film according to  claim 1 , wherein the additive is a compound capable of lowering Rth λ  in such a range as fulfilling numerical formulae (3) and (4):
   ( Rth   λA   −Rth   λ0 )/ A≦<− 1.0  Numerical formula (3)     0.01≦A≦30  Numerical formula (4)   
     wherein Rth λA  indicates Rth λ  by nm of a cellulose acylate film containing A % by mass of the compound capable of lowering Rth λ ; Rth 0  indicates Rth λ  by nm of a cellulose acylate film not containing the compound capable of lowering Rth λ ; and A indicates an amount by mass % of the compound capable of lowering Rth λ  referring a mass of a starting polymer of the cellulose acylate film as to 100. 
   
   
       10 . The cellulose acylate film according to  claim 1 , which the additive is a compound capable of lowering |Re 400 −Re 700 | and |Rth 400 −Rth 700 | in an amount of 0.01 to 30% by mass based on a solid content of a starting polymer of the cellulose acylate film. 
   
   
       11 . The cellulose acylate film according to  claim 1 , which has a film thickness of 10 to 120 μm. 
   
   
       12 . A method of producing a cellulose acylate film according to  claim 1 , which comprises:
 casting a cellulose acylate solution containing a solvent on a support to provide a film,   stripping off the film from the support; and   drying the film,   wherein the film in the stripping has an amount of the solvent of 50 to 200%.   
   
   
       13 . A method of producing a cellulose acylate film according to  claim 1 , which comprises:
 casting a cellulose acylate solution containing a solvent on a support to provide a film,   stripping off the film from the support; and   drying the film at a temperature of 120 to 160° C.   
   
   
       14 . An optically compensatory film comprising:
 a cellulose acylate film according to  claim 1 ; and   an optically anisotropic layer having Re 630  of 0 to 200 nm and |Rth 630 | of 0 to 400 nm.   
   
   
       15 . A polarizing plate comprising: a polarizer; and a protective film of a cellulose acylate film according to  claim 1 . 
   
   
       16 . A liquid crystal display comprising a cellulose acylate film according to  claim 1 .